This invention relates to a welding apparatus and method and, more particularly to a long reach welding torch suitable for welding irregularly shaped objects and a method for selecting shape of the torch.
Automation of welding processes by robotic devices is desirable generally to increase manufacturing efficiency including one or more welding steps. Gas tungsten arc welding (GTAW or TIG, i.e., tungsten inert gas welding) is often employed for automated or robotic welding because the electrode employed is nonconsumable. The robotic device, to properly perform the weld, must be either programmed or equipped with various sensors to automatically or semi-automatically guide the robotic device. This becomes particularly cumbersome where the workpieces have various three-dimensional shapes. Furthermore, these shapes sometimes have manufacturing tolerances. Additionally, the tip of the welding apparatus can become bent or otherwise transformed during use. To properly weld these shapes, a robotic welding device must be able to position the tip of the welding apparatus at a suitable distance and angle in relation to the joint to be welded.
Welding from the inside of a workpiece often requires that an access opening be cut in the workpiece to allow access to the interior. However, this is time consuming and requires that the access opening be closed when the welding from the inside is completed, which generally requires another welding operation.
Therefore, a need exists for a welding apparatus and method suitable for welding irregular shapes, and particularly for welding irregular shapes from the inside of a workpiece.
In a method for determining a shape for a long reach device, e.g., a torch, suitable for use within a portion of an object along a joint curve, e.g., a weld joint, the long reach device is dissected into a discrete number of portions. A first degree of freedom, e.g., in the azimuth direction, is identified between each of the portions, the first degree of freedom having a first movement range. The first movement range is discretized (or divided) into a predetermined number of intervals. A total number of possible shapes is determined, based on the total portions of the long reach device having the first movement range discretized into a predetermined number of intervals. A representation of the joint curve, including the portion of the object, is generated and a representation of the long reach device having one of the possible shapes is compared with the representation of the portion of the object. One of the possible shapes is deemed acceptable if less than a predetermined portion of the representation of the long reach device interferes with the representation of the portion of the object.